This patch complements the original patch for MDEV-18896 that prevents
conversions to semi-joins in tableless selects used in INSERT statements
in post-5.5 versions of the server.
The test case was corrected as well to ensure that potential conversion
to jtbm semi-joins is also checked (the problem was that one of
the preceeding testcases in subselect_sj.test did not restore the
state of the optimizer switch leaving the 'materialization' in the state
'off' and so blocking this check).
Noticed an inconsistency in the state of select_lex::table_list used
in INSERT statements and left a comment about this.
This patch fixes an invalid read in fill_effective_table_privileges
triggered by a grant_version increase between a PREPARE for a
statement creating a view from I_S and EXECUTE.
A tmp table was created and free'd while preparing the statement,
TABLE_LIST::table_name was set to point to the tmp table
TABLE_SHARE::table_name which no longer existed after preparing was
done.
The grant version increase made fill_effective_table_privileges
called during EXECUTE to try fetch the updated grant info and
this is where the dangling table name was used.
triggers are opened and tables used in triggers are prelocked in
open_tables(). But multi-update can detect what tables will actually
be updated only later, after all main tables are opened.
Meaning, if a table is used in multi-update, but is not actually updated,
its on-update treggers will be opened and tables will be prelocked,
even if it's unnecessary. This can cause more tables to be
write-locked than needed, causing read_only errors, privilege errors
and lock waits.
Fix: don't open/prelock triggers unless table->updating is true.
In multi-update after setting table->updating=true, do a second
open_tables() for newly added tables, if any.
it always required UPDATE privilege on views, not being able to detect
when a views was not actually updated in multi-update.
fix: instead of marking all tables as "updating" by default,
only set "updating" on tables that will actually be updated
by multi-update. And mark the view "updating" if any of the
view's tables is.
Always set SERVER_MORE_RESULTS_EXIST when executing stored procedure statements
If statements produce a result, EOF packet needs this flag (SP ends
with an OK packet). IF statetement does not produce a result, affected rows
count are part of the final OK packet.
If an IN-subquery is used in a table-less select the current code
should never consider it as candidate for semi-join optimizations.
Yet the function check_and_do_in_subquery_rewrites() improperly
checked the property "to be a table-less select". As a result
such select in IN subquery was used in INSERT .. SELECT then
the IN subquery by mistake was registered as a semi-join subquery
and convert_subq_to_sj() was called for it. However the code of
this function does not assume that the parent select of the subquery
could be a table-less select.
1. Always drop merged_for_insert flag on cleanup (there could be errors which prevent TABLE to be assigned)
2. Make more precise cleanup of select parts which was touched
Disable LOAD DATA LOCAL INFILE suport by default and
auto-enable it for the duration of one query, if the query
string starts with the word "load". In all other cases the application
should enable LOAD DATA LOCAL INFILE support explicitly.
The fix for "MDEV-17698 MEMORY engine performance regression"
previously fixed this problem.
- Adding the test for MDEV-17724
- Re-recording wrong results for tests:
* engines/iuds/r/insert_number
* engines/iuds/r/update_delete_number
which started to fail since MDEV-17698
mysql_upgrade used to convert all columns of mysql.db to
utf8_general_ci and then back to utf8_bin. In two separate ALTER's.
This failed if UNIQUE indexes in mysql.db contained entries
that differ only in the letter case.
derived table / view by equality
Now rows of a materialized derived table are always put into a
temporary table before join operation. If BNLH is used to join this
table with the result of a partial join then both operands of the
join are actually put into main memory. In most cases this is not
efficient.
We could avoid this by sending the rows of the derived table directly
to the join operation. However this kind of data flow is not supported
yet.
Fixed by not allowing usage of hash join algorithm to join a materialized
derived table if it's joined by an equality predicate of the form
f=e where f is a field of the derived table.
The problem was that join_columns creation was not finished due to error of notfound column in USING, but next execution tried to use join_columns lists.
Solution is cleanup the lists on error. It can eat memory in statement MEM_ROOT but it is an error and error will be fixed or statement/procedure removed/altered.
truncate incorrect values in convert_period_to_month() so that
PERIOD_DIFF never returns a value outside of 2^23 range.
And, for safety, increase buffer sizes for int10_to_str
to be sufficienly big for any int10_to_str result.
We do not accept:
1. We did not have this problem (fixed earlier and better)
d982e717ab Bug#27510150: MYSQLDUMP FAILS FOR SPECIFIC --WHERE CLAUSES
2. We do not have such options (an DBUG_ASSERT put just in case)
bbc2e37fe4 Bug#27759871: BACKRONYM ISSUE IS STILL IN MYSQL 5.7
3. Serg fixed it in other way in this release:
e48d775c6f Bug#27980823: HEAP OVERFLOW VULNERABILITIES IN MYSQL CLIENT LIBRARY
In this case we are setting the field Item_func_eq::in_eqaulity_no for the semi-join equalities.
This helps us to remove these equalites as the inner tables are not available during parent select execution
while the outer tables are not available during materialization phase.
We only have it set for the equalites for the fields involved with the IN subquery
and reset it for the equalities which do not belong to the IN subquery.
For example in case of nested IN subqueries:
SELECT t1.a FROM t1 WHERE t1.a IN
(SELECT t2.a FROM t2 where t2.b IN
(select t3.b from t3 where t3.c=27 ))
there are two equalites involving the fields of the IN subquery
1) t2.b = t3.b : the field Item_func_eq::in_eqaulity_no is set when we merge the grandchild select into the child select
2) t1.a = t2.a : the field Item_func_eq::in_eqaulity_no is set when we merge the child select into the parent select
But when we perform case 2) we should ensure that we reset the equalities in the child's WHERE clause.
with join_cache_level>2
During muliple equality propagation for a query in which we have an IN subquery, the items in the select list of the
subquery may not be part of the multiple equality because there might be another occurence of the same field in the
where clause of the subquery.
So we keyuse_is_valid_for_access_in_chosen_plan function which expects the items in the select list of the subquery to
be same to the ones in the multiple equality (through these multiple equalities we create keyuse array).
The solution would be that we expect the same field not the same Item because when we have SEMI JOIN MATERIALIZATION SCAN,
we use copy back technique to copies back the materialised table fields to the original fields of the base tables.
This patch fixes another problem introduced by the patch for mdev-4817.
The latter changed Item_cond::fix_fields() in such a way that it could
call the virtual method is_expensive(). With the first its call
the method saves the result in Item::is_expensive_cache. For all next
calls the method returns the result from this cache. So if the item
once was determined as expensive the method always returns true.
For subqueries it's not good, because non-optimized subqueries always
is considered as expensive.
It means that the cache should be invalidated after the call of
optimize_constant_subqueries().
LOSS
ANALYSIS:
=========
When converting from a BLOB/TEXT type to a smaller
BLOB/TEXT type, no warning/error is reported to the user
informing about the truncation/data loss.
FIX:
====
We are now reporting a warning in non-strict mode and an
appropriate error in strict mode.
Due to a legacy bug in the code of make_join_statistics() detecting
so-called constant tables could miss some of them in rare queries
that used RIGHT JOIN. As a result these queries had execution plans
different from the execution plans of the equivalent queries with
LEFT JOIN.
Besides starting from 10.2 this could trigger an assertion failure.
In this issue we are using derived_with_keys optimization and we are using these keys to do a hash join which is incorrect.
We cannot create keys for dervied tables whose keyparts have types are of BLOB or TEXT type. TEXT or BLOB columns can only be
indexed over a specified length.
When the definition of the index used for hash join was created
in create_hj_key_for_table() it could cause memory overwrite
due to a bug that led to an underestimation of the number of
the index component.
MDEV-16512 Server crashes in find_field_in_table_ref on 2nd
execution of SP referring to non-existing field
Problem was in the natural join code that it changed TABLE_LIST and
Item_fields but didn't restore changed things if things goes wrong
and was not able to re-execute after failure.
Some of the problems could have been avoided if we would have run
fix_fields before doing natural join transformations.
Fixed by marking functions complete AFTER they had executed, instead at
start.
I had also to change some tests that checked if Item_fields are usable.
This doesn't fix all known problems, but at least avoids some crashes.
What should be done in the near future is to mark the statement in the SP
as 'not re-executable' and force a reparse of it on next execution.
Reviewer: Sergei Petrunia <psergey@askmonty.org>